Exposure time setting device for a photographic camera with a frosted glass plate precision setting and an electronic time setting arrangement

ABSTRACT

A device for the light dependent setting of the exposure time of a photographic camera having a frosted glass pane observation plane for controlling the exposure adjustment and an electronic time setting arrangement comprising resistance-capacitance members which are separately selectable in accordance with the photographic sensitivity of the exposed medium. The device has a funnel-shaped housing with an opening for the entry of light. The housing is adapted to be placed upon the frosted glass pane of the camera. Disposed inside the housing is a light sensitive element that is a component of a bridge circuit which also has an adjustable resistance and a meter movement coil. With these components, the resistance value corresponding to the degree of brightness of the frosted pane is determined and delivered to the circuit of the electronic time setting device by a switch arrangement and a wire connection.

nited States Patent Bonk Feb. 22, 1972 [54] EXPOSURE TIME SETTING DEVICE3,257,919 6/1966 Sato et a1. ..95/l0 C FOR A PHOTOGRAPH; (3 AMER A3,291,022 12/1966 Brown ..95/10 0 x 3,063,354 11/1962 3,l00,429 8/1963Koch..... 3,227,056

WITH A FROSTED GLASS PLATE PRECISION SETTING AND AN ELECTRONIC TIMESETTING ARRANGEMENT Inventor: Heinrich Sylvester Bonk, Calmbach, Ger

many

Prontor-Werk Alfred Gauthier, GmbH, Calmbach Black Forest, GermanyFiled: June 24, 1969 Appl. No.: 836,081

Assignee:

Foreign Application Priority Data July 2, 1968 Germany ..P 17 72 777.4

References Cited UNITED STATES PATENTS Matulik et al. ..95/ 10 C ..95/l0C l/ 1966 Lieser ..95/l0 C 3,460,451 8/1969 Starp et a] ..9s/10 c 7/1970Mehlitz et al. ..9s/1o 3,518,927,

FOREIGN PATENTS OR APPLlCATlONS 54,186 11/1967 Germany ..9s/s3 E 162,0492/1958 Sweden ..356/226 Primary Examiner-Joseph F. PetersAttorney-March, Le Fever & Wyatt [57] ABSTRACT A device for the lightdependent setting of the exposure time of a photographic camera having afrosted glass pane observation plane for controlling the exposureadjustment and an electronic time setting arrangement comprisingresistancecapacitance members which are separately selectable inaccordance with the photographic sensitivity of the exposed medium. Thedevice has a funnel-shaped housing with an opening for the entry oflight. The housing is adapted to be placed upon the frosted glass paneof the camera. Disposed inside the housing is a light sensitive elementthat is a component of a bridge circuit which also has an adjustableresistance and a meter movement coil. With these components, theresistance value corresponding to the degree of brightness of thefrosted pane is determined and delivered to the circuit of theelectronic time setting device by a switch arrangement and a wireconnection.

7 Claims, 4 Drawing Figures PAltNIEnrzazz um 24 4 Hlllllllllll INVE NTOR Heinrich S. Bonk B Y 7 March, Le Fe ver, 144mm Lazar A T7 OR NE YSEXPOSURE TIME SETTING DEVICE FOR A PIIOTOGRAPIIIC CAMERA WITH A FROSTEDGLASS PLATE PRECISION SETTING AND AN ELECTRONIC TIME SETTING ARRANGEMENTThis invention relates to an exposure time setting device for aphotographic camera with a frosted glass plate precision setting and anelectronic time setting arrangement. The invention provides an apparatusfor light dependent exposure setting with an electronic time settingarrangement with resistance-capacitance segments referred to as RCmembers.

Photographic cameras of the type referred to above which permit thepresetting of the exposure time merely by hand have already beendeveloped with a supplementary device equipped with a photoresistance.By means of this supplementary device, the exposure time can becontrolled automatically depending on the light conditions. Since thissupplementary device is fitted on the outside of the camera, such as onan external toe fitting, the use of the camera is limited when it comesto taking pictures of very close objects or in microscope photography.The reason is that in such special picture taking not only thedifference between the angle of view and the measurement angle, but alsothe parallax between camera objective and photoresistance introduceerrors which may result in improper exposure.

It is an object of this invention to provide a supplementary device fora camera of the type referred to above with the aid of which it ispossible to set the camera to the exact exposure time depending upon thelight condition prevailing at the frosted glass plate.

It has now been found that the foregoing and related objects can bereadily attained by means of a device in the form of a funnel-shapedhousing with a light entry opening that can be attached to the frostedglass plate of the camera. Within the housing there is a light sensitiveelement which is part of an electrical bridge that includes a variableresistance and a moving coil instrument. With the aid of this bridge,the resistance corresponding to the light condition of the frosted glasspane can be determined and fed into the circuit of the electronic timesetting device by means of a switching arrangement and a wireconnection. This arrangement makes it possible by relatively simplemeans to close a gap in the application possibilities of a camera with afrosted glass pane precision setting and an electronic time settingdevice, inasmuch as these cameras, with the aid of the proposedattachment, can now be used also for very special tasks, such as takingclose photographs and microscope photographs. By measuring the lightcondition at the frosted glass pane, the difference in the measurementangle-angle of view and the parallax are eliminated. Additionally, whenusing a bellow extension or adapter rings, the extension factor to beconsidered in the exposure time is entered automatically into themeasurement result, which means that in this case the cumbersomecalculation of exposure time becomes unnecessary.

In order to be able to use the exposure time setting device whenevernegative material of differing film sensitivity is to be exposed,several condensers, each graduated to different load capacity relativeto others, are provided to .allow for the sensitivity of the plate orfilm material. The condensers are set according to the definitesensitivity value of the plate or film material by a setting deviceserving this purpose. Easy use of the device is achieved by theprovision of a common setting key for the switch arrangement.

A particularly advantageous design of the exposure time setting deviceprovides a setting key which upon release blocks the variableresistance. Thus an accidental change in the setting of the variableresistance after the measuring process is securely avoided insurprisingly simple fashion.

Other objects and advantages will be readily apparent from the followingdetailed specification and the drawings showing an illustrativeembodiment of the invention wherein:

FIG. 1 is a partial top view of a photographic camera with frosted glassplate inserted in the backwall and with the exposure time setting deviceof this invention mounted on the frosted glass plate.

FIG. 2 is aperspective view of the setting device.

FIG. 3 is a side view of the setting device.

FIG. 4 is a diagrammatic view of the electric circuitry of the settingdevice, the dotted lines representing a mechanical connection for thecommon actuation of the change switches.

Referring now in detail to the drawings, FIG. 1 illustrates the housingof a photographic camera, designated by the reference numeral I whichcarries in the backwall a frosted glass pane 2 fitted for the precisionsetting of the objective. Furthermore, the camera is equipped with anelectronic time setting device which is designed in a known manner andtherefore not illustrated, as an electronic trip circuit havingtransistors as principal components and RC members to provide fixedexposure times. The electronic time setting device can be placed in theshutter housing 3. To set the exposure time desired, an indicator 4 ispositioned opposite one of the values shown on the time exposure scale30 fitted to the shutter housing 3 and the resistance controlling theexposure time set thereby becomes part of the circuit of the electronictime setting device. The indicator 4 can also be changed to a setting Ain which all RC-members of the electronic time setting device areswitched off.

As can be seen further from the drawing, it is possible to place uponthe frosted glass pane 2 in the backwall of the camera a device whichenables the operator to set the exposure time exactly according to thelight condition prevailing at the frosted glass pane. In the illustratedembodiment, this device is formed by a funnelor cone-shaped housing 6,which has an aperture 6a to allow the entry of light, the aperture 60being adapted to the image aperture of the camera I. A photoresistance 8is provided in the funnel-shaped hollow space of housing 6 and aconvergent lens 9 is placed before this photoresistance. Thephotoresistance is a component of a bridge circuit which is located inthe housing 6 and which includes an adjustable resistance 10. Theschematic drawing of this bridge circuit is illustrated in FIG. 4. Onearm of the bridge contains the photoresistance 8 and the adjustableresistance I0 while the other arm of this circuit contains two fixedresistors of equal ohmic value. In the diagonal of the bridge is amoving coil instrument 14 which is used as a balancing apparatus.

As further illustrated in FIG. 4, three switches 8,, S and S, areassigned to the bridge circuit and can be operated simultaneously. Thebridge circuit is connected to a battery B by means of the switches S,and S The switch S serves to connect the adjustable resistance 10located in one of the arms of the bridge either with the other arm orwith a conductor 16 to which several condensers C, through C, of varyingcapacity are connected. The latter are provided in view of the differingsensitivity of negative materials. By means of a slide contact 18 one ofthe condensers C, through C, can be electrically connected to aconductor 19. Point 20 of the bridge circuit is attached to a conductor21, which in turn can be connected to the battery B by the switch 5,. Aconductor 22 is also connectable to the battery B by the switch S Theaforementioned conductors are grouped in a cable 23 which comes from thehousing 6 and by means of a plug 24, the cable 23 can be connected to anoutlet fitted on the camera which in turn is connected to the electronictime setting device located in the shutter housing.

A tumable knob-ring 26 attached to housing 6 is provided to adjust theresistance 10. The slide contact 18 can be moved by a further knob-ring27 which bears a sensitivity scale 27a The values of this scale 27a haveto be set against a fixed indicator 28 provided on the device. Thebalancing apparatus 14 shown schematically in FIG. 4 has a pointer 14a,which as illustrated in FIG. 2 is visible behind a window 6b and workswith a fixed indicator 60. To operate the previously mentioned switches8,, S and S;,, a button 30 is mounted on the housing 6. This button canactuate the movable contact parts of these switches by means of amechanical connection indicated in FIG. 4 merely by dotted lines.

The operation and functioning of the above described exposure timesetting device is as follows:

For microscope photography or taking pictures of very close objects withthe exposure time set with the help of the aforementioned device, thedevice illustrated in FIGS. 1-4 is attached to the camera with itsopening facing the frosted glass pane 2 and connected by the cable 23 tothe electronic time setting apparatus outlet on the camera side. Theindicator 4 on the shutter 3 is placed in the setting position A whichcauses the RC members of the electronic time setting arrangement to beswitched off. Thereafter the shutter is opened, and for the duration ofthe measuring process it is kept in the open position. This isaccomplished by operating the special opening device or 8" deviceusually present in shutters of plate cameras. For the purpose ofmeasuring the brightness at the frosted glass pane 2, the button 30 ispressed which causes movement of the switches S S and S into the dottedposition in FIG. 4. In this position the bridge circuit is connected tothe battery B and the adjustable resistance 10 is brought into thecircuit. The light that falls through the objective opening upon thephotoresistance 8 causes a deflection of the balancing apparatus 14proportionate to the light intensity on the frosted glass pane 2. Byturning knob-ring 26 the variable resistance 10 is set to the value ofthe photoresistance 8, that is the ring 26 is turned until the pointer14a of the balancing apparatus returns to the center position marked bythe indicator 6c. Thereupon the button 30 is released causing theswitches 5,, S and S to return to the position shown in FIG. 4 by solidlines. In this position, the battery B is connected through theconductors 21 and 22 to the electronic time setting device in theshutter. Moreover, the resistance 10 set to the value of photoresistance8 is also included in the circuit of the electronic time setting devicethrough the conductor 16. The device is then removed from the frostedpane and the shutter is closed. Then, instead of the frosted pane 2, thenegative material to be exposed in inserted. Thus, an exposure time isset for the following exposure process that corresponds exactly to thebrightness measured at the frosted pane. The result is a perfectlyexposed picture.

When using negative material of differing sensitivity it is merelynecessary to set the knob 27 with the corresponding value on the scaleto the indicator 28. Thereby the condenser assigned to the specificsensitivity value is tapped by means of the contact slide 18. To takedifferent film sensitivities into consideration, a neutral wedgeinserted ahead of photoresistance 8 may also be used. In this case onlyone condenser would be required. If finally one wishes to work withfrosted panes of different optical density, then the indicator 28 couldbe adjustable opposite a corresponding scale, for the purpose of takingthis factor into consideration.

In addition a blocking device can be connected to the button 30 whichwould block the setting mechanism for the adjustable resistance 10 whenthe button is not pressed, and would thereby preclude accidentalshifting in the setting of this resistance.

lclaim:

l. A device for the illumination dependent setting of the exposure timein a photographic camera with a frosted glass pane for an observationplane for controlling precision adjustment and an electronic timesetting arrangement containing resistance and capacitive elementssupported in a funnelshaped housing having an opening for the entry oflight, said housing being adapted to be placed on the frosted glass paneof the camera, a light sensitive element disposed in said housing, abridge circuit for determining the resistance value corresponding to thedegree of brightness of the frosted glass pane; said bridge circuitincluding said light sensitive element, an adjustable resistance and ameter movement coil; and circuit means connectable to said bridgecircuit, said circuit means including a switch arrangement andconductive means for transmitting to the circuit of said electronic timesetting arrangement of the camera the resistance value corresponding tothe degree of brightness of said frosted glass pane.

2. The device of claim 1 further comprising, in order to take intoconsideration the sensitivity of the photographic surface, a pluralityof capacitor elements which are graduated in size relative to each otheraccording to their load ca acity, and ineluding ad usting contact meansfor selective y connecting selected individual capacitor elements tosaid circuit means to establish the exposure sensitivity value to thatof the photographic surface employed.

3. The device of claim 1 wherein said switch arrangement is controlledby a common setting button.

4. The device of claim 3 comprising in addition a setting button tocontrol the inclusion of said adjustable resistance upon the release ofsaid button.

5. A device for the illumination dependent setting of the exposure timein a photographic camera with a frosted glass pane for an observationplane for controlling precision adjustment and an electronic timesetting arrangement containing resistance and capacitive elementsincluding a housing adapted to be placed on the frosted glass pane ofthe camera, said housing having an opening for the entry of light fromsaid frosted glass pane, a light sensitive element disposed in saidhousing, a bridge circuit means for determining the resistance value ofthe light sensitive means corresponding to the degree of brightness ofthe frosted glass pane; said bridge circuit having a variable resistancein one of its arms and said light sensitive element in another adjacentarm and a fixed resistor in each other arm and a moving coil meterconnected in the diagonal between the junctions of the fixed resistorsand that of the variable resistance and the light sensitive element; andcircuit means including a plurality of capacitor elements and aplurality of individually selectable switches for transmitting to thecircuit of said electronic time setting arrangement of the camera theresistance value corresponding to the degree of brightness of saidfrosted glass pane.

6. The device of claim 5 wherein one of said switches selectivelyconnects said arm having said adjustable resistance with a resistor inanother arm in one position and with a capacitor element in anotherposition, and wherein in order to take into consideration thesensitivity of the photographic surface, the plurality of capacitorelements are graduated in size relative to each other according to theirload capacity and wherein an adjusting control switch contact means isprovided for selectively connecting a selectable one of said capacitorelements to said circuit means to match the sensitivity value of thephotographic surface employed.

7. The device of claim 6 wherein said plurality of control switches areoperable by a common unicontrol setting button.

1. A device for the illumination dependent setting of the exposure timein a photographic camera with a frosted glass pane for an observationplane for controlling precision adjustment and an electronic timesetting arrangement containing resistance and capacitive elementssupported in a funnel-shaped housing having an opening for the entry oflight, said housing being adapted to be placed on the frosted glass paneof the camera, a light sensitive element disposed in said housing, abridge circuit for determining the resistance value corresponding to thedegree of brightness of the frosted glass pane; said bridge circuitincluding said light sensitive element, an adjustable resistance and ameter movement coil; and circuit means connectable to said bridgecircuit, said circuit means including a switch arrangement andconductive means for transmitting to the circuit of said electronic timesetting arrangement of the camera the resistance value corresponding tothe degree of brightness of said frosted glass pane.
 2. The device ofclaim 1 further comprising, in order to take into consideration thesensitivity of the photographic surface, a plurality of capacitorelements which are graduated in size relative to each other according totheir load capacity, and including adjusting contact means forselectively connecting selected individual capacitor elements to saidcircuit means to establish the exposure sensitivity value to that of thephotographic surface employed.
 3. The device of claim 1 wherein saidswitch arrangement is controlled by a common setting button.
 4. Thedevice of claim 3 comprising in addition a setting button to control theinclusion of said adjustable resistance upon the release of said button.5. A device for the illumination dependent setting of the exposure timein a photographic camera with a frosted glass pane for an observationplane for controlling precision adjustment and an electronic timesetting arrangement containing resistance and capacitive elementsincluding a housing adapted to be placed on the frosted glass pane ofthe camera, said housing having an opening for the entry of light fromsaid frosted glass pane, a light sensitive element disposed in saidhousing, a bridge circuit means for determining the resistance valuE ofthe light sensitive means corresponding to the degree of brightness ofthe frosted glass pane; said bridge circuit having a variable resistancein one of its arms and said light sensitive element in another adjacentarm and a fixed resistor in each other arm and a moving coil meterconnected in the diagonal between the junctions of the fixed resistorsand that of the variable resistance and the light sensitive element; andcircuit means including a plurality of capacitor elements and aplurality of individually selectable switches for transmitting to thecircuit of said electronic time setting arrangement of the camera theresistance value corresponding to the degree of brightness of saidfrosted glass pane.
 6. The device of claim 5 wherein one of saidswitches selectively connects said arm having said adjustable resistancewith a resistor in another arm in one position and with a capacitorelement in another position, and wherein in order to take intoconsideration the sensitivity of the photographic surface, the pluralityof capacitor elements are graduated in size relative to each otheraccording to their load capacity and wherein an adjusting control switchcontact means is provided for selectively connecting a selectable one ofsaid capacitor elements to said circuit means to match the sensitivityvalue of the photographic surface employed.
 7. The device of claim 6wherein said plurality of control switches are operable by a commonunicontrol setting button.